Two stage grease gun

ABSTRACT

A portable grease gun with a dual pressure output capability which can be selectively changed by the user with little effort. The larger diameter plunger is slidable within a plunger retainer. The larger diameter plunger has a bore through them in which a smaller diameter plunger is slidable. The smaller diameter plunger moves when an actuating lever is operated to compress grease in the grease gun. The larger diameter plunger may be adjusted to remain static during operation of the actuating lever or it may be adjusted to move during all or part of the compression stroke of the actuating lever. A high pressure can be generated by movement of the smaller diameter plunger alone, or a high flow volume can be generated by movement of the smaller and larger diameter plungers in unison.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.11/106,417 titled Two Stage Grease Gun, filed on Apr. 14, 2005, with theUnited States Patent and Trademark Office. The disclosure of applicationSer. No. 11/106,417 is hereby incorporated in its entirety.

BACKGROUND OF THE INVENTION

The present invention pertains to portable grease guns, whether manuallyoperated or driven by air power or by electric batteries. Typical handoperated grease guns include a piston which forces grease from a nozzle,the grease being fed to the compression chamber from an attached mountedbarrel containing bulk grease or a grease cartridge. Most existinggrease guns provide only one output pressure of the grease expressedfrom the gun.

Frequently the user of a grease gun encounters a grease zerk which willnot accept grease because it is seized or clogged. In that case, littlecan be done without replacing the zerk to correct the problem. One priorart grease gun requires changing position of the handle to adjust themechanical advantage. This device cannot provide the 4:1 ratio pressureincrease needed to overcome a resistant zerk. Another prior art greasegun uses a complex labyrinth and a mechanical switch to engage ordisengage a ball check valve to vary pressure of grease exiting thegrease gun. This device does not permit supply to the grease gun from anattached barrel and therefore the portability and versatility of thedevice is limited.

The foregoing problems are addressed by the present two stage grease guninvention.

BRIEF SUMMARY OF THE INVENTION

A portable grease gun is provided with a dual pressure output capabilitywhich can be selectively changed by the user with little effort. Thegrease gun includes a plunger assembly which includes a larger diametervolume plunger which is selectively coupled longitudinally to a plungerextension by screw threads. The length of the volume plunger with theplunger extension attached may be varied by inserting the extension intothe bore of the volume plunger a greater or lesser amount. This isaccomplished by rotating the plunger extension relative to the volumeplunger thereby moving the coupled end of the plunger extension in andout of the screw threads within the bore of the volume plunger. Thevolume plunger and its plunger extension are received in a longitudinalpassageway of a plunger retainer which limits the longitudinal movementof the volume plunger, and prevents rotational movement of the volumeplunger relative to the plunger retainer. A smaller diameter pressureplunger is slidable within the bore through the volume plunger and theattached plunger extension. The plunger assembly is longitudinallyreceived within a bore of the grease gun body.

An actuating lever is pivotal upon the grease gun body which includesthe plunger assembly within the longitudinal bore through the body. Thelever includes a push block which abuts the plunger assembly to urge thepressure plunger and selectively the volume plunger toward the outputorifice of the grease gun.

The desired pressure of the grease expelled from the grease gun body iscontrolled by selective rotation of the plunger extension to shorten orextend the effective length of the volume plunger and plunger extensioncombination. When the plunger extension is maximally received into thebore of the volume plunger, the volume plunger is prevented fromlongitudinal travel. However, the smaller diameter pressure plunger mayslide along the bores of the volume plunger and the plunger extension,traveling into the compression chamber to pressurize grease at a highpressure and low volume. When the plunger extension is minimallyreceived within the bore of the volume plunger, the effective length ofthe volume plunger and plunger extension combination is increased,allowing the volume plunger to be moved into the compression chamberwhen the push block of the actuating lever applies force to the end ofthe pressure plunger and the plunger extension, causing both the volumeplunger and the pressure plunger to move in concert.

When the plunger extension is moved to an intermediate insertion withinthe bore of the volume plunger, the actuation of the lever will firstcause movement of the pressure plunger alone, providing a high pressuregrease delivery during the first part of the stroke of the actuatinglever and subsequently a low pressure grease delivery when the pushblock begins to abut the plunger extension and the pressure plungertogether, thereby urging both the pressure plunger and the volumepressure together toward the output body of the grease gun. The greasegun can therefore be used to apply high pressure grease to a resistantzerk during the first part of the stroke of the actuating lever and thento deliver high volume grease at low pressure after the resistance ofthe zerk is overcome.

It is a primary object of the invention to provide a portable grease gunwhich can be adjusted to deliver grease at high pressure and low volumeor at low pressure and high volume. It is a further object of theinvention to provide a portable grease gun which can be adjusted toovercome a clogged or seized zerk and then to inject grease into thecorrected zerk at lower pressure and higher volume. It is also an objectof the invention to provide a grease gun which is easily adjusted forpressure output by the user without tools. It is an additional object ofthe invention to provide an easily manufactured grease gun which willexpel grease at more than one pressure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is an exploded view in perspective of a preferred embodimentgrease gun according to the present invention.

FIG. 2 is a cross section of the preferred embodiment of the inventionshown with the actuating lever fully retracted and with the plungerassembly adjusted for delivery of grease at high pressure and low volumeas the actuating lever is moved toward the handle.

FIG. 3 is a cross section of the preferred embodiment of the grease gunadjusted as in FIG. 2 but with the actuating lever abutted to the handleof the grease gun and the pressure plunger advanced to the outlet checkvalve.

FIG. 4 is a cross section of the preferred embodiment of the inventionshown with the actuating lever fully retracted and with the plungerassembly adjusted for delivery of grease at low pressure and high volumeas the actuating lever is moved toward the handle.

FIG. 5 is a cross section of the preferred embodiment of the grease gunadjusted as in FIG. 4, but with the actuating lever abutted to thehandle of the grease gun and with both the pressure plunger and thevolume plunger fully advanced into the compression chamber of the greasegun.

FIG. 6 is a cross section of the preferred embodiment of the inventionshown with the actuating lever fully retracted and with the plungerassembly adjusted for delivery of grease at high pressure during thebeginning portion of the stroke of the actuating lever and at lowpressure during the remainder of the stroke.

FIG. 7 is a cross section of the preferred embodiment of the grease gunadjusted as in FIG. 6 with the actuating lever actuated part way suchthat the high pressure portion of the stroke is completed and theplunger assembly is in position for delivery of grease at high volumeand low pressure for the remainder of the stroke of the actuating levertoward the handle.

FIG. 8 is a cross section of the preferred embodiment of the grease gunadjusted as in FIG. 6 with the actuating lever shown abutted to thehandle with the pressure plunger advanced maximally into the compressionchamber and with the volume plunger advanced partially into thecompression chamber.

FIG. 9 is an isometric view of a grease gun according to an alternativeembodiment of the present invention.

FIG. 10 is a side elevational view of the grease gun of FIG. 9.

FIG. 11 is a front elevational view of the grease gun of FIG. 9.

FIG. 12 is an exploded view of the grease gun of FIG. 9.

FIG. 13 is a partial cross-section view of the grease gun of FIG. 9adjusted to a high pressure mode with the actuating lever in a retractedneutral position.

FIG. 14 is a partial cross-section view of the grease gun of FIG. 9adjusted to a high pressure mode with the actuating lever in a closedposition.

FIG. 15 is a partial cross-section view of the grease gun of FIG. 9adjusted to a high volume mode with the actuating lever in a retractedneutral position.

FIG. 16 is a partial cross-section view of the grease gun of FIG. 9adjusted to a high volume mode with the actuating lever in a closedposition.

DETAILED DESCRIPTION OF THE INVENTION

Reference is drawn to FIGS. 1-8 and specifically to FIG. 1, initially.FIG. 1 discloses a grease gun body 1 according to the present inventionwith the plunger assembly 27 thereof shown in exploded view. Plungerassembly 27 is received within longitudinal bore 28 of grease gun body1. Plunger assembly 27 comprises a volume plunger 3 which is slidablyreceived within an elongate hollow cylindrical plunger retainer 9.Plunger retainer 9 is provided with an opening 29 on its sidewall 30into which guide pin 17 is received. Volume plunger 3 includes anelongate slot 31 into which guide pin 17 may extend such that volumeplunger 3 is prevented from rotation relative to plunger retainer 9,while remaining free to move longitudinally within plunger retainer 9over a range limited by a stop within plunger retainer 9.

O-ring 23 and backup ring 25 are received on inner end 32 of plungerretainer 9. Opposing outer end 33 of plunger retainer 9 is threaded tobe received in threaded bore 28. Slots 56 are provided on outer end 33to aid threading plunger retainer 9 into bore 28.

Plunger extension 11 is received in longitudinal bore 36 of plungerretainer 9 and is coaxially retained to volume plunger 3, at a selecteddepth, by selective insertion of inner end 34 of plunger extension 11into passageway 35 of volume plunger 3. Threads 55 on inner end 34 ofplunger extension 11 mate with internal threads 54 within passageway 35of volume plunger 3. Plunger extension 11 with volume plunger 3 attachedcoaxially thereto is biased toward push block 4 by volume plunger spring12. Bearing ring 18 provides a sliding surface between shoulder 53 ofplunger extension 11 and volume plunger spring 12.

By rotating plunger extension 11 clockwise or counterclockwise, theeffective length of the coaxially connected plunger extension 11 andvolume plunger 3 may be selected. Thumb wheel 48 on plunger extension 11facilitates rotation thereof by the user.

Pressure plunger 2 is slidably received within the longitudinal bore 37of plunger extension 11 and the longitudinal passageway 35 of volumeplunger 3 and is biased toward push block 4 by pressure plunger spring13. Pressure plunger 2 comprises inner end 41 from which extends needle42 having pressure face 43 on free end 44 thereof.

Volume plunger 3 is slidable over a limited range within thelongitudinal bore 36 of plunger retainer 9. Guide pin 17 is received insidewall 30 of plunger retainer 9 and rides in slot 31 of volume plunger3.

The range of longitudinal retroactive movement of volume plunger 3 islimited by an internal stop 57 (see FIG. 6) spaced apart from inner end32 of plunger retainer 9. Volume plunger 3 comprises a counterbore 50extending from outer end 49 part way therethrough. Counterbore 50accommodates inner end 34 of plunger extension 11 while the remainder ofpassageway 35 is reduced in size to accommodate body 38 of pressureplunger 2 for sliding movement therealong.

To reach into and be slidable within passageway 35 of volume plunger 3,pressure plunger must pass along bore 37 of plunger extension 11.Pressure plunger spring 13 biases head 39 of pressure plunger 2longitudinally outward along bore 37 while volume plunger spring 12biases the interconnected plunger extension 11 and volume plunger 3longitudinally outwardly along bore 36. Inward longitudinal travel ofvolume plunger 3 is limited by contact of the thumb wheel 48 againstouter end 33 of plunger retainer 9.

Referring now to FIGS. 2 and 3, grease gun 26 further comprises anactuating lever 5 pivotally retained to grease gun body 1 by hinge pin46. Push block 4 is retained to actuating lever 5 by spring pin 10allowing push block 4 to rotate about spring pin 10 in order to maintaina flat surface against outer end face 40 of pressure plunger 2.

Handle 8 depends from grease gun body 1 at an approximate perpendicularto the longitudinal axis of grease gun body 1. Output body 6, which maybe a nozzle, is received within longitudinal bore 28 grease gun body 1at output end 22 and includes an output check ball 20 biased by outputspring 15 which is retained in output body 6 by output check screw 16.

Grease gun body 1 further comprises a barrel mount 47 which houses inletvalve body 7, which includes valve spring 14 which biases inlet checkball 21. A barrel 24 may be selectively mounted to grease gun body 1 atbarrel mount 47. Grease gun 26 is shown with the inner end 34 of plungerextension 11 substantially fully inserted into counterbore 50 of volumeplunger 3. In this condition, grease gun 26 is adjusted to delivergrease at a high pressure.

In FIG. 2, the grease gun 26 as shown is ready to begin to expel greasefrom compression chamber 45 through output body 6 at high pressure, thatis, in the range of about 10,000 psi. Actuating lever 5 has beenretracted from handle 8 allowing pressure plunger spring 13 to urgepressure plunger 2 to follow push block 4 as it retreats from grease gunbody 1 as it is carried on spring pin 10 on actuating lever 5. Volumeplunger 3 is maximally retracted from compression chamber 45 whileneedle 42 of pressure plunger 2 remains partially within compressionchamber 45. Compression chamber 45 may be filled with grease whichpasses inlet check ball 21 from barrel 24.

FIG. 3 discloses the position of the plunger elements after actuatinglever 5 has been moved back to rest against handle 8. Volume plunger 3remains in the same position as in FIG. 2 while pressure plunger 2 hasfurther protruded into compression chamber 45 with needle 42 thereofinserted within the output duct 51 thereby forcing grease fromcompression chamber 45 past outlet check ball 20. The force upon outerend face 40 of pressure plunger 2 exerted by push block 4 compressespressure plunger spring 13.

Referring now to FIGS. 4 and 5, grease gun 26 is illustrated incondition to expel a large volume of grease at a low pressure. FIG. 4shows the location of pressure plunger 2 and volume plunger 3 whenactuating lever 5 is maximally retracted from handle 8. In the conditionof grease gun 26 in FIGS. 4 and 5, plunger extension 11 has beenretracted from counterbore 50 of volume plunger 3 by selective rotationof plunger extension 11 by manipulation of thumb wheel 48 thereofeffectively unscrewing inner end 34 of plunger extension 11 fromcounterbore 50. This effectively extends the length of the combinedvolume plunger 3 and plunger extension 11, allowing outer end 52 ofplunger extension 11 to extend from longitudinal bore 28 and fromplunger retainer 9. As should be understood, as actuating lever 5 startsto move toward handle 8, push block 4 forces both pressure plunger 2 andvolume plunger 3 toward output body 6 across compression chamber 45.This movement causes volume plunger 3 combined with pressure plunger 2to force a large volume of grease at low pressure past output check ball20 against output spring 15.

After actuating lever 5 has been fully rotated into abutment on handle8, as shown in FIG. 5, volume plunger 3 as well as pressure plunger 2have traversed compression chamber 45 toward output duct 51 causing lowpressure grease to pass along output duct 51 and pass output check ball20 of output body 6.

FIGS. 6-8 illustrate the adjusted position of grease gun 26 in whichplunger extension 11 is mounted to volume plunger 3 midway intocounterbore 50 thereof. By selective rotation of plunger extension 11 bymanipulation of thumb wheel 48, inner end 34 may be moved into anintermediate position along counterbore 50 of volume plunger 3. In thisposition grease gun 26 is capable of delivering grease at high pressureor at high volume depending on the extent of retraction of the actuatinglever 5. Specifically, in FIG. 6, actuating lever 5 is shown fullyretracted such that grease gun 26 is ready to expel grease at highpressure, such as when a resistant zerk must be overcome. Volume plunger3 is stationed at a rest position determined by the retractive urgingcreated by volume plunger spring 12 as limited by internal stop 57 ofplunger retainer 9. Pressure plunger 2 is retracted from output body 6by the urging of pressure plunger spring 13 but such retraction islimited by the abutment of head 39 thereof against push block 4.

As seen in FIG. 7, as actuating lever 5 has moved from a fully retractedposition partway toward handle 8, pressure plunger 2 has been urged intocompression chamber 45 while volume plunger 3 has remained in its restposition as seen in FIG. 6. As needle 42 of pressure plunger traversescompression chamber 45, grease therein is forced at high pressure pastoutput check ball 20 to be expelled into a zerk (not shown) which wouldbe inserted into a coupler and extension (not shown) attached to outputbody 6 proximal to output check screw 16. Therefore, high pressuregrease could be forced into a resistant zerk to overcome its clog orseizure. From the position of actuating lever 5 seen in FIG. 7, greasegun 26 is in condition to deliver grease at low pressure as actuatinglever 5 continues to be moved toward handle 8.

FIG. 8 illustrates the position of volume plunger 3 and pressure plunger2 after actuating lever 5 has completed its travel and come intoabutment with handle 8. Volume plunger 3 has advanced substantially intocompression chamber 45 coincident with movement of pressure plunger 2,with plunger assembly 27 propelling grease from compression chamber 45through output body 6 at high volume and low pressure.

Therefore it should be understood that grease gun 26 may be adjusted todeliver grease at high pressure and low volume when inner end 34 ofplunger extension 11 is maximally inserted into counterbore 50 of volumeplunger 3. However, when inner end 34 of plunger extension 11 isminimally inserted into counterbore 50 of volume plunger 3, grease gun26 will expel grease at low pressure and high volume. Furthermore,plunger assembly 27 may be adjusted such that a first portion of thestroke of actuating lever 5 from its fully retracted position willdeliver grease at high pressure while a remaining portion of the strokeof the actuating lever 5 will deliver grease at low pressure. Thisadjustment is made by varying the depth of insertion of inner end 34 ofplunger extension 11 into counterbore 50 of volume plunger. By selectiveadjustment, the proportion of stroke of the actuating lever 5 whichcauses the grease gun 26 to deliver high pressure grease may be varied,that is, the shorter the effective length of the combination of thevolume plunger 3 and the plunger extension 11, the larger the proportionof stroke of the actuating lever 5 from its fully retracted positionwhich will deliver high pressure grease from grease gun 26. As theeffective length of the volume plunger 3 and plunger extension 11increases, the smaller the proportion of the stroke of actuating lever 5from full retraction will be which causes the grease gun 26 to deliverhigh pressure grease, with the remainder of the compression stroke ofactuating lever 5 toward handle 8 causing low pressure grease to beexpelled from grease gun 26.

An additional embodiment of a two-stage grease gun 100 according to thepresent invention is illustrated in FIGS. 9-16. This gun 100 may be fedwith a reusable barrel that may be bulk loaded with grease (typicallyabout 16 ounces) or loaded with a disposable cartridge (typicallycontaining about 14.5 ounces). This gun 100 can develop over 10,000 psiof pressure in a high pressure, or boost mode. The high pressure issometimes required to unblock a plugged grease fitting (zerk). Once theblockage is overcome, the gun 100 can be switched to a low pressure highvolume mode to deliver the nominal amount of grease—preferably about oneounce of grease in twenty-two (22) strokes. The gun 100 uses twodiameters of pistons with the smaller alternately able to slide insidethe larger or engage the larger and translate both in unison in order toaccomplish the two-stages. This gun 100 preferably has a handle 140 longenough to permit two-handed operation.

As best seen in FIGS. 9-12, the gun 100 includes a gun body 101 that hasan outlet valve 109 for dispensing grease. The gun body 101 may beformed from die cast aluminum, injection molded plastic, or by otherknown materials and mechanisms. A grease reservoir 150, such as areusable barrel or a disposable cartridge is connected to generally to alower portion of the body 101. An actuating lever 102 is pivotallyattached at the rear of the gun body 101. Preferably the handle 140 islong enough to permit two-handed operation. The actuating lever 102 ispinned to the body 101 by pivot member 130. A toggle lever 121 may beadjusted up or down about sixty degrees (60°) to move between the boostmode and the volume mode. In the embodiment shown in FIGS. 9-16, the gun100 is in the boost mode when the toggle lever 121 is adjusted to theupper position shown in FIG. 9, and can be adjusted to the volume modeby moving the toggle lever 121 downwardly.

The inner working of the gun 100 can best be seen in FIG. 12, whichprovides an exploded view of the gun 100 from FIG. 9. Outlet valve 109and inlet valve 115 attach to front and lower portions of the body 101respectively. According to one embodiment, the outlet valve 109 andinlet valve 115 are metal fittings that are molded into a plastic body101. Alternatively, the outlet valve 109 and inlet valve 115 may bethreaded such that they screw into their respective positions. A pistonhousing 104 is provided within the gun body 101 to house a pistonassembly. According to one embodiment, the housing 104 is molded intothe body 101 and is threaded for mated engagement with the outlet valve109.

A volume piston 108 is slidably provided within piston housing 104. Thevolume piston 108 has an opening in its front face. Boost piston 107 isalso slidably provided within housing 104, and has a front portion thatextends through the opening in the front face of the volume piston 108.A retaining ring 120 is snap fit on the end of the boost piston 107 toretain the front portion of the boost piston 107 on the front, oroutlet, side of the front face of the volume piston 108. Stop ring 119is threaded into the housing 104 to limit rearward travel of the volumepiston 108. A piston spring 105 is provided between the stop ring 119and a shoulder formed on the inner piston 107 to urge the inner piston107 rearwardly away from the outlet 109. The rearward travel of theinner piston 107 is constrained by the volume piston 108 bearing againstthe stop ring 119 and the retaining ring 120 bearing against the volumepiston 108.

The rear portion of the volume piston 108 is provided with a slot orrecessed portion 141. The inner piston 107 is provided with a keyportion 142 that is milled flat, such that when the inner piston isrotated to a mating alignment, the key portion 142 will fit into therecessed portion 141, permitting the inner piston 107 to slide forwardrelative to the volume piston 108. When the key portion 142 is not inmating alignment with the recessed portion 141, the key portion 142 willpress against the rear of the volume piston 108, causing the innerpiston 107 and volume piston 108 to move forward together as a unit. Theinner piston 107 can be rotated within the housing 104 by adjustingtoggle lever 121. Pin 118 engages housing 104 and volume piston 108 toprevent rotation of the volume piston 108 relative to the housing. Thevolume piston 108 is provided with a longitudinal slot to receive thepin 118, such that longitudinal sliding the volume piston 108 relativeto the housing 104 is permitted.

Additional structure of the gun 100 can be seen in the cross-sectionview of FIG. 13. A gasket 103 may be provided to seal the greasereservoir 150 (not shown in FIG. 13, see FIG. 10) with the gun body 101.The inlet valve body 115 is sealed to the housing 104 by a seal ring116. A ball 114 and spring 113 are used to provide a one-way valvearrangement within inlet valve body 115. The outlet valve 109 works asdescribed above with respect to the other embodiments of the presentinvention. In particular, a set screw 112 is used to adjust theresistance of spring 111 bearing against ball 110. A seal ring 117 isprovided to seal the outlet valve body 109 to the housing 104.

Sealing ring 106 seals the inner piston 107 with the volume piston 108.Likewise, sealing rings 124 and 125 seal the volume piston 108 withhousing 104.

Bearing 126 is mounted to actuating lever 102 by pin 127 to bear againstthe rear face of inner piston 107. Preferably the bearing 126 isrotatably mounted to the lever 102.

FIGS. 13 and 14 show the gun 100 adjusted into a boost mode. In FIG. 13,the actuating lever 102 is in a neutral position, and the inner andvolume pistons 107 and 108 are withdrawn to their rearward mostpositions, such that the cavity behind the outlet 109 contains a fullload of grease. In FIG. 14, the lever 102 has been squeezed (in aclockwise direction as shown), to press the bearing 126 against theinner piston 107, causing the inner piston to translate forward towardsthe outlet 109. Because the toggle switch 121 is in the boost mode, thekey portion 142 of the inner piston 107 is matingly aligned with therecessed portion of the volume piston 108, and the inner piston 107 willslide through the volume piston 108, driving the front portion of theinner piston 107 towards the outlet 109. A volume of greasecorresponding to the volume displaced by the inner piston 107 is forcedthrough the outlet 109. Because the force of the actuating lever 102 istransmitted through the small surface area of the front face of theinner piston 107, a high outlet pressure can be generated if a cloggedzerk is encountered. If the actuating lever is released, the spring 105will return the inner piston 107 and the actuating lever 102 to theposition of FIG. 13. It should be appreciated that as the inner piston107 withdraws back to the neutral position, the resulting vacuum willdraw in additional grease through the inlet valve 115.

FIGS. 15 and 16 show the gun 100 adjusted into a high volume mode. InFIG. 15, the actuating lever 102 is in a neutral position, and the innerand volume pistons 107 and 108 are withdrawn to their rearward mostpositions, such that the cavity behind the outlet 109 contains a fullload of grease. In FIG. 16, the lever 102 has been squeezed (in aclockwise direction as shown), to press the bearing 126 against theinner piston 107, causing the inner piston to translate forward towardsthe outlet 109. Because the toggle switch 121 is in the volume modeposition, the key portion 142 of the inner piston 107 bears against therear of the volume piston 108, causing the two pistons 107 and 108 tomove forward as a unit. As shown, the outer diameter of the volumepiston 108 is about twice that of the inner piston 107. Accordingly, thecombination of the volume piston 108 and the inner piston 107 displaceabout four times as much volume during a single stroke as compared tothe inner piston 107 alone. Correspondingly, the combination of thevolume piston 108 and the inner piston 107 can generate about one fourthof the pressure based on the same input force applied by the actuatinglever 102. If the actuating lever 102 is released, the spring 105 willreturn the inner piston 107, the volume piston, and the actuating lever102 to the position of FIG. 15.

Accordingly, grease gun 100 may be fed from a 16 oz barrel, and candevelop over 10,000 psi of pressure. This pressure is sometimes requiredto unblock a plugged grease fitting. Once the blockage is overcome, thegun 100 can be switched to the volume mode to deliver the nominal amountof grease—preferably about one ounce of grease in 22 strokes. Thefeature that allows this is primarily the use of two diameters of pistonwith the smaller alternately able to slide inside the larger or engagethe larger and translate both in unison.

The foregoing description of the invention has been presented forpurposes of illustration and description and is not intended to beexhaustive or to limit the invention to the precise form disclosed.Modifications and variations of the embodiments are possible in light ofthe above disclosure or such may be acquired through practice of theinvention. The embodiments illustrated were chosen in order to explainthe principles of the invention and its practical application to enableone skilled in the art to utilize the invention in various embodimentsand with various modifications as are suited to the particular usecontemplated. It is intended that the scope of the invention be definedby the claims appended hereto, and by their equivalents.

1. A grease gun comprising a grease gun body having a passagewaytherethrough, an actuating lever pivotal upon the grease gun body, afirst plunger longitudinally slidable within the passageway over alimited distance, the first plunger having a longitudinal passagewaytherethrough, a second plunger rotatably received in the longitudinalpassageway of the first plunger, the second plunger being rotatablebetween a high pressure orientation wherein the second plunger willslide within the first plunger and a nominal orientation wherein thesecond plunger moves in unison with the first plunger, movement of theactuating lever from a retracted position towards a closed position withthe second plunger in a high pressure orientation effects movement ofthe second plunger within the longitudinal passageway, movement of theactuating lever from the retracted position towards the closed positionwith the second plunger in a nominal orientation effects movement of thefirst and second plungers in unison.
 2. The grease gun of claim 1further comprising a grease reservoir for grease connected to a portionof the grease gun body.
 3. The grease gun of claim 1, wherein the highpressure orientation supplies a pressure sufficient to unblock a pluggedgrease fitting.
 4. The grease gun of claim 1, wherein the first plungercomprises a first diameter and the second plunger comprises a second,smaller diameter.
 5. The grease gun of claim 1 in which the grease gunbody is formed from components selected from the group consisting ofdie-cast aluminum, zinc, magnesium and injection molded plastic.
 6. Thegrease gun of claim 1 further comprising a lever for selection of atleast one of the high pressure orientation and the nominal orientation.7. The grease gun of claim 6, wherein the lever is rotatable.
 8. Thegrease gun of claim 7, wherein the rotatable lever is rotated 60 degreesto move between the high pressure orientation and the nominalorientation.
 9. The grease gun of claim 1 in which the first plunger isprovided with a recessed portion and the second plunger is provided witha key portion such that it will mate with the recessed portion.
 10. Thegrease gun of claim 1 further comprising a spring return operablyconnected to at least one of the first plunger and the second plunger.11. A grease gun comprising: a grease gun body having a passageway; anactuating lever operably attached to the grease gun for displacement ofgrease; a first plunger slidable within the passageway, the firstplunger having a longitudinal passageway; and a second plunger rotatablyreceived in the longitudinal passageway of the first plunger, the secondplunger being rotatable between a high pressure orientation wherein thesecond plunger will slide within the first plunger and a nominalorientation wherein the second plunger will move in unison with thefirst plunger.
 12. The grease gun of claim 11, further comprising alever for selection between the high pressure orientation and thenominal orientation.
 13. The grease gun of claim 12 wherein the lever isrotatable.
 14. The grease gun of claim 11, in which the actuating leveris operably connected to the second plunger such that movement of theactuating lever with the second plunger in the high pressure orientationeffects movement of the second plunger within the longitudinalpassageway of the first plunger.
 15. The grease gun of claim 11, inwhich the actuating lever is operably connected to the second plungersuch that movement of the actuating lever with the second plunger in thenominal orientation effects movement of the second plunger in unisonwith the first plunger.